Fast pyrolysis is a process during which organic biomass materials, such as, wood waste, agricultural waste, etc. are rapidly heated to about 450° C. to about 600° C. in the absence of air using a process reactor. Under these conditions, organic vapors, pyrolysis gases and solid fragments of char and the like are produced. The vapors are condensed to form a biomass-derived pyrolysis oil. A biomass-derived pyrolysis oil can be burned directly as fuel for certain boiler and furnace applications, and can also serve as a potential feedstock in catalytic processes for the production of fuels in petroleum refineries. Biomass-derived pyrolysis oils have the potential to replace up to 60% of transportation fuels, thereby reducing the dependency on conventional petroleum and reducing its environmental impact.
However, biomass-derived pyrolysis oils are a complex, highly oxygenated organic liquid having properties that currently limit its utilization as a biofuel. For example, biomass-derived pyrolysis oils are typically contaminated with char and other insolubles produced during biomass pyrolysis. Char contributes to thermal instability of the oil. The char content is correlated with increases in viscosity, phase separation, and/or solids formation during storage. Separation of the char fragments from the biomass-derived pyrolysis oil has proven very difficult. For example, conventional liquid filtration is difficult as the liquid biomass-derived pyrolysis oil can have a gel-like consistency.
Additionally, metals in the biomass-derived pyrolysis oil limit its commercial applications. Metals are present in the solid fragments and are also dissolved in the biomass-derived pyrolysis oil as metal cations. The metals contribute to the ash content of the oil upon combustion. It is desirable to reduce and/or minimize the ash content in the biomass-derived pyrolysis oil because such ash raises the total ash and particulate emissions when the biomass-derived pyrolysis oil is burned for consumption as a fuel. Environmental restrictions may limit such total emissions. In addition, when the biomass-derived pyrolysis oil is used as feedstock in catalytic processes to make transportation fuel, the metals in the oil foul downstream equipment and inhibit or inactivate catalysts.
Accordingly, it is desirable to provide methods and apparatuses for forming a biomass-derived pyrolysis oil having a relatively low metal concentration. In addition, it is desirable to provide methods and apparatuses for removing solid fragments, such as char and other insolubles to form a biomass-derived pyrolysis oil with increased thermal stability. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.